This invention is an improved approach to baling and packaging of lint cotton in cotton ginning facilities hereinafter referred to as “cotton gins”. For more than two hundred years the accepted method of packaging lint cotton for storage or transport at the cotton gin has been the bale. The “bale” is the preferred form of presentation used by the textile industry as a basis for blending fibers. At the cotton gin final packaging of lint cotton for shipment has historically been the function of the bale press. Many versions of bale presses producing various sizes and densities of cotton bales have been introduced to the ginning industry over the years. Today two preferred bale “types” dominate the global ginning industry. They are the Gin Universal Density and High Density bales.
Modern baling presses must meet design requirements to satisfy one or the other of the bale types. Domestically, that press is the Universal Density Baling Press; a press capable of producing a 500 lb. bale of lint cotton 55 inches in length by 20-21 inches in width and 26-30 inches thick. Such presses use hydraulics to drive the primary and secondary axes, to wit the main compression cylinder[s] and tramper cylinder respectively, although some presses currently in operation continue to use mechanical trampers.
The purpose of the tramper in the scheme of the modern baling press is to pack lint cotton from the lint slide into the press box. Press boxes on all Universal Density Presses are approximately equal in box opening size; width from side-to-side (54 inches+/−) and front-to-back (20 inches+/−). Box length, however, can vary depending on whether the press is up-packing or down-packing, whether boxes come with retaining dogs or without, the available press compressive tonnage capacity and manufacturer's preference. A significant number of modern conventional baling presses incorporate retaining dogs 30 (FIG. 3) into their press box designs. Retaining dogs have been a necessary evil due to the natural resiliency of compressed cotton lint. In cases where conventional press boxes are short relative to tramper compressive capability and/or tramper stroke length, retaining dogs are the critical component for keeping lint from springing out of the top of the press box. Retaining dogs are also intrusive. They conflict with the uniform flow of lint cotton during the tramping process. They present a mechanical challenge in that they must (depending on design) be removed from the internal regions of the press box during certain phases of the baling cycle. The presence of retaining dogs equates to additional cost and maintenance. For these reasons elimination of retaining dogs is gaining popularity in modern press designs albeit to the detriment of additional box length, deeper foundations for up packing presses (FIG. 1), higher roof lines for down packing presses (FIG. 2), and increases in hydraulic cylinder length, both that of the ram (primary axis) and tramper (secondary axis). The effect to date of eliminating retaining dogs has been to add to the cost of material in the manufacturing process, increase the cost of installation, plus additional pump and horsepower requirements in the application process.
Current gin baling presses incorporate basic PLC logic with discreet inputs and outputs as the control platform. While the industry has been well served by these control systems they are dated and fall short of meeting requirements for high speed operation with smooth accurate control. This invention advances the controls and hydraulics of the tramper and pusher to a new level of high speed operation all the while maintaining smooth accurate control. In order to accomplish this it is critical to have knowledge of the position of the tramper and pusher at all times. This allows for closed loop position based speed control. A closed loop position based control, unlike time based systems and/or fixed position systems used by current art, is not sensitive to the presence (or lack) of cotton. In order to achieve the type of control necessary accurate position feedback and high performance hydraulic valves are required.
One aspect of controlling the tramper and pusher axes is proportional hydraulic control technology. By combining proportional control technology with infinite position feedback this invention features a true closed loop control system. As a new feature for the cotton ginning industry, this invention includes proportional control valves with onboard electronics and spool position feedback for high performance. It also uses mango-restrictive linear transducer technology for accurate position feedback. One problem faced when using proportional valves on high speed machines is the cost associated with large valves, and the large valves inability to provide finite control at the low end of the flow range. The new technology on this press includes a high flow slave valve that is proportionally controlled by the flow rate through the master proportional valve. This slave valve is preset to open at a given flow rate and then continue to open proportionally to the increased flow through the main valve. This allows for the use of a small proportional valve in conjunction with one or more slave valves to accommodate very high flows during mid stroke. The relatively small proportional valve is then used as a standalone control for the low flow range.
One consequence of high-speed operation in current state of the art baling press technology is large inductive loads associated with oversized direct connected horsepower at the primary hydraulic movers. The motors are oversized in order to meet peak power needs, such as final bale compression, last few strokes of the tramper, etc.). The majority of the time these large motors are idling. Where pump motors are operating below full load, there is a loss in motor efficiency. It is not uncommon for hydraulic power unit designers to oversize motors and thereby build inefficiencies into the system. As a result of these “built in inefficiencies” gins pay higher demand and power factor charges. This invention uses a unique method to address these issues through an optimized horsepower control. With the availability of pressure feedback from both the tramper and press axes coupled with load sense pump controls and a proportional directional valve, the horsepower controller becomes a series of mathematical calculations within the press program. The end result of this unique control scheme is the ability to vary the power requirements of each axis as needed while at the same time optimize the available horsepower.
Another consequence of high-speed operation in current state of the art baling press technology is the difficulty associated with determining and maintaining a set bale weight. Feedback from force transducers, both electrical and hydraulic, have traditionally been used to approximate real-time bale density or weight. The short-comings of these devices are they are not accurate and are influenced by variables beyond the control of the system and/or operator, the least of which is variations in moisture content. This invention features position and pressure transducers that provide an accurate representation of real-time conditions throughout the formation of the bale. In addition, data tabulated from the transducer feedback along with bale density history and moisture content data provide this invention with the ability, through a series of algorithms, to anticipate true bale weight and meter the final charges of cotton by varying run time and speed of a lint feeding device 4.
This invention is a short box press utilizing a hydraulically driven actuator to pre-compress approximately 500 pounds of ginned lint cotton in such a manner no additional mechanical retaining-devices are required to hold the lint in the short box. It is the object of this invention to overcome the short-comings associated with long press boxes and/or short press boxes requiring lint retaining devices. A further object of this invention is to introduce feedback from various analog inputs to 1) control acceleration and deceleration of the hydraulic axes at their respective limits, to 2) determine both actual bale weight and bale moisture content via an industrial programmable computer (PC) program utilizing input data from various field devices and pre-configured algorithms, and 3) through load sensing, reduce direct connected horsepower requirements to an optimum.